Most human diseases and adaptive traits in natural populations are controlled by multiple interacting genes with small, and environmentally sensitive effects. Determining what loci contribute to variation in complex traits, how they interact with each other and the environment, and what molecular polymorphisms cause the variation in phenotypes, are of fundamental importance for human health and understanding the evolutionary process. Research on the genetic architecture of quantitative traits requires expertise with concepts and methodology in the traditionally separate disciplines of molecular, developmental, quantitative and population genetics, statistics and molecular evolutionary theory. The goal of this program is to provide this interdisciplinary training. The training faculty has combined expertise in all of these disciplines, have active research programs focusing on experimental and statistical genetics, and interact extensively. Support is requested for four predoctoral trainees for five years. The University strongly supports this training program, and has committed four additional traineeships. The training program will follow the Ph.D. program in the Department of Genetics. Trainees will be selected and their progress monitored annually by the Executive Committee. Interdisciplinary training will be stressed, with advanced courses in at least three of the major disciplines required. Trainees will select their major advisor(s) and advisory committee after three laboratory rotations among the training faculty in their first semester. Collaborative research projects will be encouraged. Trainees will receive formal training in ethics and professional development, including oral scientific presentation, and will participate in an annual student symposium as part of the training program.